External Magnetic Field Strength Research Articles

Thermo-Magnetic properties of non-relativistic particles under the effect of energy-dependent Hellmann potential

This manuscript presents an analysis of the thermal and magnetic properties of particles moving in two dimensions under the influence of an external magnetic field and Aharanov-Bohm flux, considering an energy-dependent Hellmann potential. The energy eigenvalue is obtained using the asymptotic iteration method. Next, we model the system as a canonical ensemble and derive the partition function to acquire analytical expressions for the Helmholtz free energy, entropy, mean energy, and specific heat. We observe that an increase in the external magnetic field and AB flux generally increases the energy eigenvalues, with a stronger effect at lower flux values, while energy eigenvalues decrease with an increase in the screening parameter. Additionally, Helmholtz free energy and entropy functions are sensitive to temperature, particularly in the low-temperature regime, while specific heat exhibits a Schottky anomaly. We also compute the magnetisation and susceptibility functions, finding that both magnetisation and susceptibility increase with the external magnetic field strength and the AB flux.

Numerical simulations of a low-pressure electrodeless ion source intended for air-breathing electric propulsion

Abstract Air breathing electric propulsion (ABEP) systems offer a promising solution to extend the lifetime of very low earth orbit (VLEO) missions by using residual atmospheric particles as propellants. Such systems would operate in very low-pressure environments where plasma ignition and confinement prove challenging. In this contribution, we present results of a global plasma model (GPM) of a plasma ignited in a very low-pressure air mixture. The results are validated against experimental measurements acquired using a laboratory electrodeless ion source utilizing a resonator for plasma ignition. The device is specifically designed to operate within low-pressure environments as it holds potential applications in ABEP systems for VLEO missions. Parametric studies are carried out via GPM to investigate the resonant behavior and its implications. The potential of the model serving as a predictive tool is assessed through experimental validation against measured data, mainly investigating the extracted ion current dependency on operational pressure and external magnetic field strength. The verified model is further utilized to extrapolate additional information about the resonant plasma such as ion composition or a degree of ionization.

Micro magnetic field sensor based on bifunctional diodes

Multiple-quantum well (MQW) diodes can be used as bifunctional diodes due to the emission-detection spectral overlap. When integrated with magnetic fluids (MFs) that have tunable refractive index, they can be designed as micro magnetic field sensors. The sapphire substrate of the MQW diode chip that consists of an MQW transmitter and receiver that is directly exposed to the MF, and the external magnetic field strength is used to change the refractive index at the boundary between the sapphire and the MF, thus modulating the reflected light and realizing external magnetic field sensing. Verified by experimental measurements, the micromagnetic field sensor has a detection range of 0.001-0.05 T, a sensitivity of 127.3 µA/T, and a resolution of 4.5×10−5 T, with excellent stability and repeatability. Additionally, the sensor demonstrates good velocity resolution under dynamic magnetic fields and can detect the direction of magnetic field motion, providing significant application value.

Radiation generation from an array of magnetized anharmonic carbon nanotubes

An investigation into second-harmonic generation from magnetized anharmonic carbon nanotubes (CNTs) mounted on a silica substrate is conducted using a Gaussian laser pulse with modulated amplitude. An intense amplitude-modulated laser pulse incident on the array of CNTs displaces their electrons generating a restoration force. This restoration force is the nonlinear function of displacement of electrons, which ensures the anharmonic behavior of CNTs. Using the paraxial ray approximation, the nonlinear interaction of the incident pulse with CNTs is expressed in terms of a wave equation derived using the perturbative technique. The nonlinear current at second-harmonic frequency arises due to the perturbation of the electron density of CNTs by the ponderomotive force exerted on them by an incident pulse. Numerical outcomes validate the enhanced efficiency of the generated harmonic when considering the phenomenon of self-focusing. With the substantial optical nonlinearities of an anharmonic CNT structure, the plasmon resonance is broadened and high efficiency in generating harmonics is attained. It is seen that the augmenting of the amplitude-modulated parameter of the pulse and the external magnetic field strength enhances system nonlinearity, resulting in increased amplitude of generated second harmonics. Additionally, the effect of the heating rate of CNTs on the efficiency of the generated harmonic is also discussed.

Exploring Magnetic Attributes: Borospherene-Like and Buckminsterfullerene-Like Lattices in Monte Carlo Simulations

This study explores the magnetic properties of Borospherene-like and Buckminsterfullerene-like lattices using Monte Carlo simulation, revealing novel behaviors. The dependency of blocking temperature (T B ) on external magnetic field strength (H), linear coupling interaction (J), and biquadratic coupling interaction (K) was studied and compared between the two lattice types. Additionally, the evolution of coercive field (H C ) with J and K parameters for both lattice types was analyzed. This study highlights the unique magnetic responses of these lattices and their potential applications in magnetic research and nanotechnology.

Investigation of MHD flow balancing in electrically conductive manifolds of liquid metal blankets

In the liquid metal (LM) blanket design for magnetic confinement fusion reactors, manifolds including main and branch ducts are commonly used to direct fluids to various locations of the blanket to cool its components. The primary objective of this structural configuration is to achieve flow balancing within each branch duct. However, magnetohydrodynamic effects will cause uneven flow distribution, consequently, uncontrollable overheating phenomena in certain blanket segments may be caused by this flow distribution. To assess its impact, the influences of external magnetic fields, inlet velocities and coupling wall thicknesses on the flow partitioning in conductive manifolds are investigated in this study. The results indicate that the flow distribution among the branch ducts becomes less uniform as the external magnetic field strength increases, while varying the inlet velocity has minimal impact. In addition, increasing the coupling wall thickness leads to more even flow distribution when the rectangular branch ducts are perpendicular with the magnetic field direction. Based on above physical understanding, three controlling methods for the flow partitioning in conductive manifolds are proposed to achieve flow balancing in each branch duct and then validated through numerical simulations. The results indicate that flow balancing can be achieved by adjusting the coupling wall thickness when the rectangular branch ducts are aligned with the magnetic field direction, however, it is challenging when they are perpendicular. Furthermore, the flow balancing can be realized by a symmetrical design of the manifold with circular branch pipes and it is independent of external magnetic fields and inlet velocities. These findings will enhance the physical understanding of flow distribution patterns in conductive manifolds under strong magnetic fields, which is important for the flow control and design of manifolds in LM blankets.

Research on Spatial Magnetic Field Distribution of Magnetic Fluids Based on Microstructure.

This study focuses on the spatial magnetic field distribution of magnetic fluids, an extraordinary class of fluids composed of magnetic nanoparticles (MNPs), employing the Monte Carlo method to simulate the microstructure of magnetic fluids under an external magnetic field. On that basis, a model was established through magnetic dipole theory to delve into the spatial magnetic field distribution of magnetic fluids. The findings reveal that the application of a magnetic field leads to the formation of chain-like structures within the magnetic fluids, resulting in inhomogeneous spatial magnetic field distribution. The size and concentration of MNPs are crucial determinants that significantly affect the microstructure of magnetic fluid and its spatial magnetic field distribution. Furthermore, environmental conditions such as external magnetic field strength or temperature can also regulate the positions of MNPs within magnetic fluids and the spatial magnetic field distribution of the magnetic fluids. These observations enrich the comprehension of the fundamental mechanisms of magnetic fluids and their response to diverse factors, advancing the growing comprehension on the characteristics and applications of these remarkable magnetic fluids.

The role of non-uniform magnetization texture for magnon–magnon coupling in an antidot lattice

We numerically study the spin-wave dynamics in an antidot lattice based on a Co/Pd multilayer structure with reduced perpendicular magnetic anisotropy at the edges of the antidots. This structure forms a magnonic crystal with a periodic antidot pattern and a periodic magnetization configuration consisting of out-of-plane magnetized bulk and in-plane magnetized rims. Our results show a different behavior of spin waves in the bulk and in the rims under varying out-of-plane external magnetic field strength, revealing complex spin-wave spectra and hybridizations between the modes of these two subsystems. A particularly strong magnon–magnon coupling, due to exchange interactions, is found between the fundamental bulk spin-wave mode and the second-order radial rim modes. However, the dynamical coupling between the spin-wave modes at low frequencies, involving the first-order radial rim modes, is masked by the changes in the static magnetization at the bulk–rim interface with magnetic field changes. The study expands the horizons of magnonic-crystal research by combining periodic structural patterning and non-collinear magnetization texture to achieve strong magnon–magnon coupling, highlighting the significant role of exchange interactions in the hybridization.

Geant4 simulation of secondary photons generated by laser–solid interaction in the presence of external magnetic field

A parametric study of the average energy and scattering angle distribution of Bremsstrahlung x-ray photons generated in over-dense fuel were investigated using the Geant4 simulation toolkit in fast ignition concept. In our simulation, over-dense fuel with the mass ρc∼(300−1000)g.cm−3, and fast ignitor with the intensity I=(1021,1023)W.cm−2 and wavelength λ=(0.35,0.53)μm were considered in the presence of an external magnetic field with the strength Bext=(0−10)kT. Further, for the produced MeV electrons in pre-plasma, two types of energy distribution functions, i.e., exponential and quasi two-temperature, were considered. The simulation results show that by applying an external magnetic field strength Bext∼(1−2)kT, a smooth increase was observed in the x-ray photon average energy and a considerable increase in scattering angle and photon counts in over-dense plasma obtained, so that the peak values mostly obtained for Bext∼1kT. Meanwhile, between the two energy distribution functions for electrons, the optimal average energy and scattering angle values were obtained by considering the quasi-two-temperature energy distribution function and for the fast igniter intensity and wavelength, I=1021W.cm−2,λ=0.35μm respectively, and the fuel density ρc∼300g.cm−3. Finally, regarding to the obtained optimal average photon energy (i.e., Ebph<0.4MeV), which could be considered as minimum photon energy loss and maximum electron penetration toward the fuel, the minimum thickness of lead and concrete shields required to reduce the flux of photons to its one-tenth value were found to be 1.5 cm and 30.7 cm, respectively.

Distributed magnetic field sensor using nickel-acrylate composite coated silica optical fiber

This paper reports on the development and characterization of a distributed magnetic field sensor utilizing magnetostrictive material and the Rayleigh backscattered signal in optical fiber. The sensor consists of a single-mode fiber (SMF) coated with nickel-acrylate (Ni-Acryl) composite, fabricated using the conventional fiber drawing method. The surface morphology and the coating thickness of the Ni-Acryl were analysed using SEM. The sensor is capable of measuring variations in the strain of the fiber as the external magnetic field strength changes, with a spatial resolution of 20 cm. The experimental results revealed a linear relationship between magnetic field strength and Rayleigh frequency shift, with an average sensitivity of 22.85 MHz/mT. The magnetostrictive strain of the Ni-Acryl composite coated fiber is measured to be 36.4 με in response to the 245 mT applied magnetic field. This study highlights the potential of the developed sensor to be utilized in magnetic field sensing applications, particularly for remote sensing applications in a harsh environment.

MODELING OF THE EXTERNAL MAGNETIC FIELD OF ELECTRIC MACHINES

Powerful electric machines – such as electric generators, electric motors generate a magnetic field of great tension. These fields negatively effect on personnel and can to violate the stability of electronic equipment. To determine safe areas for workers, laying communication cables and placing sensitive electronic equipment, it is advisable to model the propagation of magnetic fields of electrical machines. This will make it possible to rationalize the placing of electrical equipment at design stages. The most common high-power electrical machines are four-pole electrical machines with a dipole-quadrupole structure of the external magnetic field. The purpose of the research is a development of models of the propagation of the external magnetic field generated by alternating current electric machines. Results of the research: it is substantiated that to simulate the propagation of the magnetic field of electric machines, it is advisable to use the Gauss equation for the magnetic scalar potential. This will make it possible to take into account the required number of spatial harmonics of the magnetic field to ensure an acceptable calculation error. An electric machine is considered in a spherical approximation. Calculations were carried out in spherical coordinates. The distances were determined in relative radii of the electric machine - the ratio of the radius of the machine to the definition of field strength. The calculations were made for two planes of spherical coordinates and a three-dimensional image was obtained. As a result of the simulation, it is possible to determine the magnetic field strength of a four-pole electric machine at selected distances and directions around the electric machine with the required accuracy. It has been established that there are points of zero external magnetic field strength around electrical machines. Verification of the simulation results was carried out using the method of full-scale measurements of the magnetic field strength around a real four-pole machine. The measurement results showed acceptable agreement with the calculated data. Conclusions: the chosen approach and the results of modeling the propagation of the external magnetic field of electrical machines can be used to design the placement of electrical equipment, taking into account the requirements for electromagnetic safety and electromagnetic compatibility of technical equipment.

Controllable light group velocity in a degenerate two-level medium under the assistance of an external magnetic field

In this work, we proposed a simple model for control of subluminal and superluminal light propagation via an external magnetic field in a lambda configuration degenerate two-level atomic medium. We show that the absorption-dispersion properties and group index under the influence of the strength of coupling laser and external magnetic fields are controlled. By changing the direction and magnitude of the magnetic field, the medium switches from transparency with normal dispersion to enhanced absorption with anomalous dispersion at the line center, corresponding with the transfer from slow light to fast light. This work may provide for the application realization of magneto-optic switches and storage devices in quantum information processing.

First principal calculation of the physical proprieties of the ternary intermetallic compound Gd2Cu2Cd for magnetic refrigeration applications

The manuscript explores the electromagnetic and magnetocaloric characteristics of the intermetallic compound Gd 2 Cu 2 C d . One of the key findings is that Gd2Cu2Cd possesses a magnetic moment of approximately 7.13 μB. The simulated magnetic properties illustrate a second-order phase transition from ferromagnetic (FM) to paramagnetic (PM) occurring at approximately 130 K. This material exhibits a substantial magnetocaloric effect (MCE) across various external magnetic field strengths. To be more specific, this transition occurs at an external magnetic field of 4.0 T, in particular, at an external magnetic field of 4.0 T, the extreme magnetic entropy change ( Δ S mag ) is measured at 3.58 J/kg.K, and the relative cooling power (RCP) reaches 28 J/kg. Notably, with an increase in the external magnetic field, the maximum value of ( ΔS mag ) increases significantly, and the Curie temperature ( T C ) shifts toward lower temperatures. These results suggest that Gd 2 Cu 2 Cd has significant potential for applications in magnetic refrigeration that leverage the magnetocaloric effect.

A tunable multitasking renal function assessment biosensor predicated on cylindrical metastructure

Chronic renal disease has become one of the world’s most serious public health problems in recent decades, leading to physical degradation, and even death. Glucose and creatinine in body fluids are important indicators used to assess renal dysfunction, but current biosensors only focus on the detection and performance improvement of a single indicator. To break through the idea limitation, a cylindrical metastructure based on indium antimonide material is proposed in this paper. It innovatively realizes the tunable multitasking renal function assessment biosensor, which is more suitable for the application of multiple medical detection scenarios. Through the control of the external magnetic field strength, the glucose concentration of 0 ∼ 400 g/L and the serum creatinine concentration of 80.9 ∼ 85.28 μmol/L can be separately detected in real-time, unlabeled, and non-destructively, which own better performance than previous renal function assessment biosensors in terms of detection range, R2, quality factor, figure of merit, and detection limit. This proposal has important reference value for promoting the detection and treatment of renal diseases, and the research of multitasking biosensors.

Magnetic circuit design for the performance experiment of shear yield stress enhanced by compression of magnetorheological fluids

The shear yield stress is an important parameter for the industrial application of magnetorheological (MR) fluids. A test equipment was designed and built to perform investigations on the behaviours of compression and shear after squeeze of MR fluids. Mathematical expression of magnetic flux density was further established. Furthermore, the magnetic field distribution of the test device based on two-coil mode and single-coil mode was simulated and compared using finite element analysis(ANSYS/Multiphysics). An experimental test system was fabricated and modified based on the final conditions and simulation results. The compression and shear after squeeze performances of MR fluids were tested. The results showed that a smaller initial gap distance or a larger compressive strain corresponds to a larger compressive stress under the same external magnetic field strength. The shear yield stress after the squeeze of MR fluids increases quickly with the increasing compression stress and the increasing magnetic flux density. This test equipment was thought to be suitable for studying the compression and shear after squeeze performances of MR fluids.

Research on magnetoelastic coupling model based on magnetic dipole theory

In this paper, a theoretical model of a magnetoelastic coupling magnetic dipole is established to analyse the influence of stress on the magnetic signal in magnetic memory testing. Based on the theory of ferromagnetism, the equivalent field strength under the combined action of stress and the magnetic field is determined and a numerical solution for the stress magnetisation of isotropic ferromagnetic materials under a weak environmental magnetic field is obtained. Based on the assumption of a double rectangular crack in a three-dimensional problem for the magnetic signal, a theoretical analysis model of a magnetoelastic coupling-type magnetic dipole is established. Based on the theory of the magnetoelastic coupling magnetic dipole, the influence factors and rules of the magnetic signal are analysed in detail. The theoretical research shows that the solution based on the theoretical model in this paper can explain some basic experimental phenomena and laws in magnetic memory inspection. The magnetic signal of a defect-free plate shows a 'horseshoe shape'. The length, width and height of the plate will affect Hx but have no effect on Hy . In addition, the lift-off value has a great influence on the magnetic signal of the plate. When the two cracks are a small distance apart, the magnetic signal of the plate is the superposition of the magnetic signals of the two cracks. For plates with cracks, the crack size, spacing, external magnetic field strength and stress will affect the magnetic signal of the plate.

Design of tunable photothermal porous thermal emitter based on nonreciprocal effect

Tunable thermal emitters have become a research hotspot for high-efficiency, low-loss novel thermal radiation devices. It has been found that the tunability of thermal radiation devices can be greatly strengthened and the efficiency of photothermal conversion enhanced through the tuning of the radiation temperature by magneto-optical microstructures. In this paper, a novel porous thermal emitter for the mid-infrared band is designed and the interconnection between nonreciprocal radiation and photothermal conversion is investigated for the first time. The three-hole column (THC) porous structure is optimized from the traditional one-hole column (OHC) porous structure. Through detailed analysis of the light incident angle, external magnetic field strength, and hole diameter, it is shown that the strong nonreciprocal radiation is due to the variation of the cavity structure parameters, which enhances the microcavity resonance effect, thereby enhancing the surface plasmon resonance (SPR) on the porous surface. The electric field contours at different positions also visualize the enhancement mechanism of SPR for nonreciprocal radiation. It has been investigated that different magnetic field strengths and porous structures have significant impact on nonreciprocal thermal tuning. The nonreciprocal system can be used to tune the local heat around the hole, and the temperature difference increase as nonreciprocal effects is greater as the magnetic field strength and input power increases. This work also provides new ideas for the application of thermal emitters and the design of energy conversion devices.

The Optimization of a Physical Factor of Hydrogen Production in Alkaline Water Electrolysis

Hydrogen fuel is an alternative to petroleum fuel as the world is changing to a zero-carbon fuel source. However, hydrogen production requires high costs and a relatively complex system. There are numerous methods available in the industry to produce hydrogen by water splitting, but alkaline water electrolysis is one of the cheapest ways of producing hydrogen gas since it only requires water, electrodes, a voltage supply, a conducting wire, some electrolytes, and a container. Besides that, water electrolysis is among the most effective ways of generating hydrogen since it utilizes renewable water and generates only pure oxygen as a by-product, indicating that it is an ecologically beneficial way of generating hydrogen gas. The water was split into hydrogen and oxygen gases by using electricity during the electrolysis process and the hydrogen gas will be produced in the cathode. The distance between the electrodes, the voltage supply, and the presence of an external magnetic field were the three parameters studied for the purpose of this study. The highest volume of hydrogen gas produced was at optimum parameters of 10 cm electrode distance, 20 V of the voltage supply, and 0.08 µT of external magnetic field strength. Although the electrolysis process accounts for a small portion of hydrogen production using the current method, researchers believe that if existing techniques are improved with appropriate materials and substances, this process will significantly benefit the community.

Supersonic Flow past a Sharp Plate with Surface Anomalous Glow Discharge in a Magnetic Field

The electrodynamic structure of an anomalous glow discharge between two plane electrodes located on the surface of a sharp plate in supersonic flow of molecular nitrogen is studied numerically in a wide range of Mach numbers using a modified ambipolar model of quasi-neutral electric-discharge plasma. The ambipolar diffusion coefficient and the effective ionization rate are modified while taking into account the external magnetic field. The problem is solved in the two-dimensional x–y formulation, when the external magnetic field strength is directed in the positive or negative direction of the z axis. The parameters of anomalous glow discharge are numerically studied in the pressure range p = 0.14–5 Torr and the voltage drops on the quasineutral current column of discharge plasma V = 30–320 V. The main problem parameters which make it possible to obtain a reasonable agreement with the available experimental data are determined.

Magnetic and magnetocaloric characteristics of the mixed Graphullerene-like structure: A theoretical study

This paper presents an investigation of the magnetic and magnetocaloric properties of a mixed Graphullerene-like nanostructure. The Blume–Capel model is employed, and Monte Carlo computations were performed using the Metropolis algorithm. The study examines various spin configurations within different parameter planes and reveals stable configurations. Furthermore, the paper analyzes magnetizations, susceptibilities, specific heat, and Binder cumulant as a function of the temperature to determine the transition temperature and characterize magnetic phase transitions in the system. The suitability of the investigated structure for magnetic refrigeration was also assessed by examining the magnetic entropy change and relative cooling power at different external magnetic field strengths. The results show a direct correlation between the external magnetic field and maximum entropy changes, indicating a significant magnetocaloric effect.